Binding and recognition in the assembly of an active BRCA1/BARD1 ubiquitin-ligase complex

Brzović, Peter S.; Keeffe, Jennifer R.; Nishikawa, Hiroyuki; Miyamoto, Κ.; Fox, David; Fukuda, Mamoru; Ohta, Tomohiko; Klevit, Rachel E.

doi:10.1073/pnas.0836054100

Cited by 324 publications

(363 citation statements)

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“…Accordingly, we mutated a critical Ile residue in the RING finger domain of the protein (DIAP1 I393A) that was reported to inactivate the autoubiquitinating activity of other ligases without affecting their RING finger structure. 33 As can be seen in Figure 3b, the mutation abolished the self-conjugating activity of the enzyme even in the presence of Reaper, the strong proapoptotic protein. Surprisingly, similar to the WT protein, I393A DIAP1 was also unstable in cells (Figure 3ci, compare lanes 4-6 to lanes 1-3).…”

Section: Resultsmentioning

confidence: 87%

Regulation of the Drosophila ubiquitin ligase DIAP1 is mediated via several distinct ubiquitin system pathways

et al. 2007

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Inhibitors of apoptosis proteins (IAPs) suppress cell death by inactivating proapoptotic regulators, and therefore play important roles in controlling apoptosis in normal and malignant cells. Many IAPs are ubiquitin ligases, and their activity is mediated via ubiquitination and subsequent degradation of their targets. Here we corroborate a previous observation that DIAP1 (Drosophila IAP1) can be degraded via a two-step mechanism: (i) limited caspase-mediated cleavage and (ii) degradation of the released fragment via the ubiquitin N-end rule pathway. Yet, we demonstrate that this pathway is not the only one involved in DIAP1 degradation, and the intact protein can be degraded independent of prior caspase cleavage. Importantly, this mode of degradation does not require the RING-finger-mediated autoubiquitinating activity of DIAP1, believed to target many RING-finger E3s for self-destruction. Our preliminary data suggest that DIAP2 mediates DIAP1 degradation, suggesting a novel regulatory loop within the apoptotic pathway. Studying the role of the autoubiquitinating activity of DIAP1, we demonstrate that it does not involve formation of Lys48-based polyubiquitin chains, but probably chains linked via Lys63. Our preliminary data suggest that the autoubiquitination serves to attenuate the ligase activity of DIAP1 towards its exogenous substrates. Recent studies indicate that ubiquitination plays an important role in regulating apoptosis. This is partially mediated by the inhibitors of apoptosis proteins (IAPs), a centrally important group of cell death regulators, many of them are ubiquitin ligases. IAPs suppress cell death by inactivating different proapoptotic factors, some by targeting them for ubiquitination and subsequent proteasomal degradation. At least eight IAPs have been identified in mammals. In Drosophila melanogaster, expression of DIAP1 and DIAP2 1 can suppress apoptosis that occurs both during normal development as well as following overexpression of proapoptotic factors such as Reaper (Rpr). 2 Loss of DIAP1 function results in early embryonic death as a consequence of massive apoptosis. [3][4][5] The IAP family is characterized structurally by one-three Nterminal copies of Baculovirus IAP Repeat (BIR) domains. DIAP1 contains two copies of BIR that bind effector and initiator caspases. In some cases, this binding leads to ubiquitination and subsequent degradation of the caspase. 2 IAP-mediated inactivation of caspases is effectively inhibited by a family of proapoptotic proteins that share an IAP-binding tetra-peptide motif at their N-termini. Among those proteins are Smac/Diablo in mammals, and Rpr, Hid and Grim (RHG) in Drosophila. It was shown that RHG proteins abrogate effectively DIAP1-mediated inactivation of Dronc and DrICE. 6 DIAP1 contains also a C-terminal RING-finger motif that serves to recruit the E2 component of the ubiquitin conjugation machinery. For RING-finger E3s, their best-characterized activity is self-ubiquitination thought to regulate their cellular level, but it is assumed th...

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Section: Resultsmentioning

confidence: 87%

Regulation of the Drosophila ubiquitin ligase DIAP1 is mediated via several distinct ubiquitin system pathways

et al. 2007

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“…BRCA1 acquires significant ubiquitin ligase activity when bound to BARD1 as a RING heterodimer (Hashizume et al, 2001). Importantly, deleterious missense mutations in the RING-finger domain of BRCA1 found in familial breast cancer kindred all abolish the ubiquitin ligase activity of BRCA1-BARD1 (Hashizume et al, 2001;Ruffner et al, 2001;Brzovic et al, 2003). This suggests a strong connection between BRCA1's ligase activity and its tumor suppressor function.…”

Section: Brca1-bard1 Ubiquitin Ligasementioning

confidence: 85%

Ubiquitin and breast cancer

2004

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The regulation of protein stability by the ubiquitinproteasome pathway is a critical issue central to the comprehension of the molecular basis of carcinogenesis. However, ubiquitin modification of target substrates signals many cellular processes other than proteolysis that are also important for the development of cancer. It is noteworthy that many proteins studied by clinical breast cancer researchers are involved in these ubiquitin pathways. This review summarizes recent works on such proteins including cyclins, CDK inhibitors, and the SCF in cell cycle control; the breast and ovarian cancer suppressor BRCA1-BARD1; ErbB2/HER2/Neu and its ubiquitin ligase c-Cbl or CHIP; and the estrogen receptor and its downstream target Efp. Understanding these pathways may provide some hints toward developing diagnostic tools and treatments for breast cancer patients.

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“…BRCA1 RING domain I26A mutant knock-in embryonic stem cells have recently been made (Reid et al, 2008). This allele abrogates BRCA1 RING domain interaction with E2 enzymes (Brzovic et al, 2003;Christensen et al, 2007), strongly reducing BRCA1 E3 activity in vitro and autoubiquitylation in vivo (Reid et al, 2008). Surprisingly, BRCA1 I26A knock-in ES cells performed homologous recombination at similar levels to cells expressing wild-type BRCA1 (Reid et al, 2008).…”

Section: Evidence For a Heterogeneous Ubiquitin Landscape At Dsbsmentioning

confidence: 99%